Most commercial typewriters are provided with an adjustable gage that may be set for different paper lengths for estimating the end margin of a typed page. If the paper is passed too near the exit position, the roller will not hold it well enough to make a straight and neat line. If a gage is not provided, or is hard to read, the typist is disciplined as the page is being completed to roll the paper to see how many more lines may be typed. This takes time and is inefficient.
The gages are expensive mechanisms in some cases, being installed in rollers or are in other cases fragile appendage carriage extensions that need be adjusted when typing and then stored or folded when the typewriter is covered. Whenever adjustability of position at different optional margins is required, then the complexity of the mechanisms increases. There are also electrically wired margin signals such as shown in U.S. Pat. No. 3,981,388, wherein switches or photocells are wired into place and operate electric pilot lamps. Such indicators are expensive and cannot be easily installed or retrofit on existing machines in the field.